An organic EL (Electroluminescence) display device is represented as an example of a display device. An organic EL display device has an organic light-emitting element (hereinafter, referred to as a light-emitting element) in each of a plurality of pixels formed over a substrate. A light-emitting element has a layer (hereinafter, referred to as an organic layer or an EL layer) including an organic compound between a pair of electrodes (cathode and anode) and is operated by supplying current between the pair of electrodes. A color provided by a light-emitting element is mainly determined by a light-emitting material in an EL layer, and light emission with a variety of colors can be obtained by appropriately selecting a light-emitting material. Arrangement of a plurality of light-emitting elements giving different colors on a substrate makes it possible to reproduce a full-color image.
An emission color and emission intensity of a light-emitting element can be also controlled by utilizing a light-interference effect in and outside the light-emitting element. For example, in Japanese patent application publications No. 2012-38555, 2008-218081, and 2006-173092, light-emission generated in an EL layer is resonated and amplified between a pair of electrodes and the light extracted from the EL layer is further resonated and amplified in an optical adjustment layer in contact with one of the pair of electrodes, by which the emission color is adjusted and the emission intensity is controlled.